DOE-2 Reference Manual Version 2.1 - DOE2.com

7. SYSTEM-AIRThe function of the SYSTEM-AIR instruction is to provide information onsystem air flow rate, both supply air and outside air. Several SYSTEM-AIRinstructions may be required if the facility is served by more than one systemand/or it is desired to conduct parametric runs.SYSTEM-AIR is a "subcommand" of SYSTEM and, as such, can be used to inputa subset of data to SYSTEM.An alternative mode for data entry is to complete and enter SYSTEM-AIRkeywords and their values directly into the SYSTEM command (if this approachis chosen, omit the SYSTEM-AIR keyword in SYSTEM).All air quantities should be input as sea level (standard) values becausethe program makes a correction for altitude. Input of air quantitiescorrected for altitude above sea level will result in a double correction.SYSTEM-AIRSUPPL Y-CFMinforms the SOL Processor that the data to follow are relatedto system air flow (supply air and outside air). A uniqueuser-defined name must be entered in the U-name field of eachSYSTEM-AIR instruction. Omission of this entry in the"subcommand" will cause an error.is the design capacity (in standard, or sea level, cfm) of thesystem air supply fan. This entry is normally omitted, unlessfan capacity is different than the maximum air flow rateassigned (using the ZONE-AIR instruction), or calculated bythe program. The program uses thlS value as the basis fordetermining part-load fan operation. Fan horsepower is calculatedon the basis of typical part-load characteristics of theselected mode of capacity control (see the keyword FAN-CONTROLin the SYSTEM-FANS instruction) and of fan static pressure andefficiency (see keywords SUPPLY-STATIC and SUPPLY-EFF in theSYSTEM-FANS instruction). Note that the static pressure entryshould also be at fan design conditions. If the SUPPLY-CFM isspecified and if the ZONE-CFMs have not been specified, thetotal supply air capacity of the system is distributed amongthe zones in proportion to their peak loads. See Sec. 0 ofth is chapter for additional discuss ion.As noted above, the program wi 11 cal cu 1 ate the des i gn flowrate when data entry for this keyword is omitted. For thosesystems that can simulate a variable rate flow (SZRH, MZS,DDS, SZCI, VAVS, RHFS, PSZ, PMZS, and PVAVS) the program willuse the default value for SIZING-OPTION to calculate thedesign flow rate, assuming certain conditions are met. Thatis if:(1) MIN-CFM-RATIO is less than 1.0,(2) SIZING-OPTION = COINCIDENT,(3) SUPPLY-CFM is not specified, and(4) only one SYSTEM is specified ~the PLANT-ASSIGNMENT,IV.213 (Revised 5/81)